YourDictionary

What does "mouth off" mean?

  1. Complain or express one's opinions loudly and indiscreetly, as in She was always mouthing off about the other members. [Slang; 1960s]
  2. Speak impudently, talk back, as in He got in trouble by mouthing off to his teacher. [Slang; 1960s]

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